Coagulase-negative staphylococci are important members of the normal aerobic microflora of human skin and mucous membranes. Normally they are not pathogenic for men. But the increase in patients with implanted plastic foreign bodies or intravascular catheters had led to a dramatic change. In these patients, coagulase-negative staphylococci are the predominant organisms causing septicemia. Special pathomechanisms are involved in the colonization of polymers by staphylococci leading to a "plastic infection". Intravascular catheters are also important factors in the origin of septicemia in premature neonates and in patients with malignant diseases, especially under cytostatic therapy. Premature or suppressed opsonophagocytosis mechanisms are responsible for the origin and maintainance of septicemia.